Two new papers from the RVC, published in the Journal of Experimental Biology, reveal how frogs are able to finely control their elongate hind legs to achieve a wide range of jump angles, from nearly horizontal to almost vertical. The two papers are led by Dr. Christopher Richards and Dr. Laura Porro, and co-authored by PhD students Amber Collings and Enrico Eberhard with contributions by Kyle Chadwick (formerly of the RVC, now based at the University of Southern California).
The team collected experimental data using high-speed cameras and ultra-sensitive force plates during jumping in Kassina maculata, the red-legged running frog. As its name suggests, this African species is capable not only of jumping but can also walk and run as well as climb and swim. This is the first study to collect such data from a “multi-functional” frog rather than a jumping specialist.
Experiments demonstrated that – despite the diverse ways Kassina can move about – its jumping performance was similar to that of frog species considered to be specialized jumpers. However, the real surprise was the extreme range of jump angles the frogs achieved. Dr. Porro said, “Some jumps were nearly horizontal, with animals skimming over the ground; in other trials, the frogs rocketed upwards almost vertically. Their capacity to jump at such a wide range of angles and distances is amazing.”
The team also used a modelling method called inverse dynamics analysis which allowed them to investigate how much each individual leg joint contributed to jumping. They found that forward power comes primarily from the hip joint while most of the vertical movement is driven by the ankle. But it is a third joint – the knee – that appears to be crucial in positioning the leg and determining the final take-off angle. This ability to jump at a wide range of angles could help this frog dynamically navigate in its complex, 3D environment and to hunt insects at night.
This interdisciplinary study combined classic experimental methods with cutting-edge biomechanical modelling techniques to reveal new insight into how major changes in anatomy are linked to the evolution of extraordinary behaviours in living animals. Future work will use these modelling methods to understand jumping in frog species specialized for swimming and burrowing, as well as in the earliest fossil frogs.